Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$162.64	13.849%	$185.164	$185.16	$185.15	$185.20
Purchase #2	$23.62	3.154%	$24.365	$24.37	$24.35	$24.40
Purchase #3	$197.98	6.209%	$210.2726	$210.27	$210.25	$210.30
Purchase #4	$189.91	13.680%	$215.8897	$215.89	$215.90	$215.90
Purchase #5	$133.83	3.102%	$137.9814	$137.98	$138.00	$138.00
Purchase #6	$34.31	10.226%	$37.8185	$37.82	$37.80	$37.80
Purchase #7	$51.57	7.234%	$55.3006	$55.30	$55.30	$55.30
7 purchase totals =	$793.86		$866.7918	$866.79	$866.75	$866.90